The proposed studies will continue investigations on the acrosomal reaction, sperm-egg binding, and generation of the fertilization envelope. We will attempt to obtain answers to the following questions. First, what are the structural differences in the jelly coat that account for its specificity in inducing the acrosomal reaction? Second, what is the chemical nature of the receptor on the egg that binds sperm? Third, what components of an isolated cell surface complex are involved in formation of the fertilization envelope?